One manner of minimizing blade tip leakage is to minimize the blade tip deflection, and thus the blade tip clearance, at engine running conditions. As such, there exist a number of both passive and active tip clearance control systems which strive to minimize and control blade tip clearance. Known passive systems used to control blade tip deflection include simply using the bore of the rotor to minimize blade tip deflections. For example, by simply adding more material to the bore, blade tip clearance can be minimized. The use of rotor bores is well suited to minimize blade tip deflections for rotors with large heavy blades, such as a fan. However, such known passive systems are much less effective at minimizing the blade tip deflections of lightweight blades used in axial compressors, particularly those high pressure compressor rotors located in the later axial stages of the compressor. Further, it is undesirable to add additional material, and therefore weight, to the hubs or bores of axial compressor rotors, particularly when the overall hub mass which results is less than is needed for minimum acceptable fatigue life. Known active tip clearance control systems tend to be relatively complex and also add weight to the rotors themselves and/or the fan or compressor stage within which they are employed.
According, an improved manner of minimizing and controlling blade tip clearance for axial rotors of gas turbine engines is sought.